Voltage overshoots due to the forward recovery time for diodes are problematic in particular in the case of very fast switching operations. With slow switching operations, the diode is usually made conducting by application of the forward bias voltage, which in the case of silicon diodes is in the region of about 0.7 V. With fast switching times, on the other hand, it already becomes noticeable that the diode becomes conductive only after a finite time has elapsed. In particular when a switch is made from reverse-biased to forward-biased, a certain period of time is required in order to distribute the charge carriers over the entire cross-section of the space charge region and, as it were, to “flood” said region with charge carriers. This finite time is critical in particular when high currents are to be conducted through the diode, when, for instance, the diode is a snubbing diode for inductances. In these cases the diode does not become conducting already at the forward bias voltage, as is critical for slow switching operations, but only at higher voltages. Said higher forward bias voltage during fast switching operations is referred to as voltage overshoot. In this case the voltage overshoot is a function of the current rise rate (mostly specified in A/μs) and can be found in the corresponding data sheets for the particular diode.
These voltage overshoots due to the forward recovery time for diodes are conventionally counteracted by an over-dimensioning of the components requiring protection. A further possibility consists in slowing down the switching operations, although this entails other disadvantages, such as, for instance, additional switching losses in switching components.